Triglyceride-glucose index as a marker of metabolic and inflammatory risk across different thyroid function states

The triglyceride-glucose (TyG) index has recently gained attention as a cost-effective and easily calculable surrogate marker reflecting insulin resistance-related metabolic risk. Given the close interplay between thyroid hormones, lipid metabolism, glucose regulation, and inflammation, evaluating the association between thyroid dysfunction and the TyG index remains clinically relevant. This study aimed to investigate variation in the TyG index across different thyroid function states-overt hypothyroidism (OH), subclinical hypothyroidism (SCH), euthyroidism (EH), and healthy controls-and to assess its associations with lipid parameters and inflammatory markers, including the CRP/albumin ratio. In this cross-sectional observational study, 222 adults were categorized according to thyroid status based on TSH and free T4 levels. The TyG index was calculated using fasting glucose and triglyceride values. Associations with lipid and inflammatory markers were evaluated, and receiver operating characteristic (ROC) analysis was performed to assess the ability of the TyG index to discriminate individuals with elevated TyG-defined metabolic risk. No statistically significant differences in TyG index levels were observed across thyroid function groups (p = 0.152). However, the TyG index showed significant positive correlations with triglyceride levels (r = 0.419, p < 0.001), CRP/albumin ratio (r = 0.342, p < 0.001), and LDL-C (r = 0.204, p = 0.009). ROC analysis demonstrated moderate discriminatory performance (AUC = 0.731; 95% CI: 0.652-0.809), identifying individuals with higher TyG levels associated with increased metabolic risk. Although TyG index levels did not differ significantly across thyroid function states, their associations with lipid and inflammatory markers suggest that the TyG index reflects metabolic and inflammatory risk profiles independent of thyroid status, rather than serving as a direct diagnostic measure of insulin resistance.